It is known to prepare polyurethane foam by the reaction of a polyisocyanate, a polyol and a blowing agent, such as a halogenated hydrocarbon, water or both, in the presence of a catalyst. One particular area of polyurethane technology is based on rigid polyurethane foams.
U.S. Pat. No. 4,469,824 to Grigsby, et al., issued Sept. 4, 1984, describes polyols produced by reacting scrap polyethylene terephthalate (PET) with diethylene glycol and one or more oxyalkylene glycols and stripping out some of the ethylene glycol present. The mole ratio of glycols to scrap PET is greater than 1.2:1. These polyols are reacted with a polyisocyanate to produce polyurethane foams.
Rigid foams generally have good insulative properties and are thus desirable for use in building insulation. As with all building materials, it is desirable to provide rigid foams that are as fire resistant as possible. One approach to this goal is to modify the polyol.
Polyisocyanate foams are a type which are considered to be fire resistant and show low smoke evolution on burning. However, polyisocyanurate foams tend to be brittle or friable. Various types of polyols have been devised to lower the foam friability, but what frequently happens is that the fire and smoke properties of the polyisocyanurate foam deteriorate. Thus, a fine balance exists between the amount and type of polyol one adds to a polyisocyanurate foam formulation in order to maintain maximum flame and smoke resistance while at the same time reach an improvement in foam friability. U.S. Pat. Nos. 4,039,487 and 4,092,276 describe attempts at this fine balance, although each has its disadvantages.
Scrap polyalkylene terephthalate, such as scrap PET, is known to be incorporated into polyurethanes. For example, U.S. Pat. No. 4,048,104 teaches that polyisocyanate prepolymers for use in polyurethane products may be prepared by combining an organic polyisocyanate with polyols which are the hydroxyl-terminated digestion products of waste polyalkylene terephthalate polymers and organic polyols. A polyol ingredient which is the digestion product of polyalkylene terephthalate residues or scraps digested with organic polyols is also described in U.S. Pat. No. 4,223,068. Another example where terephthalic acid residues are employed is outlined in U.S. Pat. No. 4,246,365 where polyurethanes are made from polyesters containing at least two hydroxyl groups and terephthalic acid residues.
In U.S. Pat. No. 4,237,238 a polyol mixture is prepared by the transesterification of a residue from the manufacture of dimethyl terephthalate with a glycol, which is then used to produce polyisocyanurate foams having a combination of a high degree of fire resistance with low smoke evolution, low foam friability and high compressive strength. The preparation of such a polyol mixture, such as from ethylene glycol and dimethyl terephthalate esterified oxidate residues, is described in U.S. Pat. No. 3,647,759. J. M. Hughes and John Clinton, in the Proceedings of the S.P.I. 25th Annual Urethane Division Technical Conference, Scottsdale, Ariz., October, 1979, describe other foams prepared from the polyols of U.S. Pat. No. 3,647,759.
Another type of polyisocyanurate foam employs a polyol blend using both amide diols and primary hydroxyl polyols to give a foam having a high reaction exotherm, making it particularly suited to the preparation of polyisocyanurate foam laminates, according to U.S. Pat. No. 4,246,364.
However, another major factor with the use of the polyester polyols described above in producing foams is that they have a limited solubility in the widely used halogenated hydrocarbon blowing agents, such as fluorocarbon 11, which is used to expand the foam and provide its insulating characteristics. It would be beneficial if a procedure could be found by which these polyester polyols could be made more soluble in halogenated hydrocarbon blowing agents.
Other methods are known for increasing the solubility of these polyester polyols in halogenated hydrocarbon blowing agents. For example, U.S. Pat. No. 4,642,319 describes modifying recycled polyethylene terephthalate polyols with aromatic amino polyols, sucrose polyols, ethoxylated alpha-methyl glucosides, alkoxylated glycerine or alkoxylated sorbitol. Additionally, U.S. Pat. No. 4,644,019 teaches modifying a recycled polyethylene terephthalate polyol with polyethoxylated nonylphenol to increase halogenated hydrocarbon solubility. However, a disadvantage with using the ethoxylates of nonylphenol is that the ethoxylate is monofunctional, that is, a monofunctional polyester is created. This polyester would act as a chain stopper during a polymerization reaction, which is not desired.